The Cryostat

Spitzer is designed to look at faint heat radiation from
objects in space. In order to be able to do this, the instruments on board must
be kept very cold so that their own heat does not interfere with the
observations. Spitzer carries a "cryostat", which uses liquid helium vapor from
the helium tank to keep the instruments cold. The cryostat holds about 360
liters of liquid helium, and can cool the instruments to temperatures as low as
1.4 degrees Kelvin (roughly -457 degrees Fahrenheit, or -272 degrees Celsius)
for more than 5 years.

The cryostat is attached to the bottom of the telescope, and
consists of the helium tank, a vacuum shell, inner and middle vapor-cooled
shields and a fluid management system. The telescope and the cryostat shell
were launched warm, and cooled down to about 35 degrees Kelvin once they were
in orbit. The cryostat vacuum shell was sealed during ground operations and
launch, and kept closed as the telescope cooled in order to protect the delicate
instruments. Once the cryostat had cooled, a door on the top of the shell was
opened to allow light into the Multiple Instrument Chamber.

The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory. This website is maintained by the Spitzer Science Center, located at IPAC on the campus of the California Institute of Technology.